The labor union CGT de los Argentinos, headed in Cordoba by Agustín Tosco, called for National strike on May 30, 1969. But in Cordoba they decided to do a general strike one day earlier, on 29 May 1969. This strike brought police repression and a civil uprising, an episode later termed the Cordobazo.[2]

Furthermore, Onganía was attempting to impose corporatism in Argentina. In this context, the important industrial hub of Córdoba was one of the experimental place of corporatinist policies, implemented by the appointed governor Carlos Caballero.

These unpopular measures led to increasing strikes and protests in the country. At the beginning of May '69, a succession of strikes and popular assemblies occurred in Córdoba, which were harshly repressed by the provincial and national military authorities of the junta.

On 13 May 1969, in Tucumán, former workers of a sugar mill took the factory and its manager as hostage, asking for overdue payments.

On 14 May, in Córdoba, automobile industry workers protested the elimination of the Saturday rest.

On 15 May, the University of Corrientes increased the price of food tickets in its cafeteria fivefold, and the ensuing protest ended up with one student, Juan José Cabral, killed by the police (see Correntinazo).

On 17 May, the student Adolfo Bello was killed during a protest in Rosario (see Rosariazo).

On 21 May, the police killed the 15-year-old student Luis Blanco during a silent march of 4,000 persons in Rosario, in commemoration of Bello's death. Rosario is declared by the authorities an emergency zone under military jurisdiction.

On 29 May 1969, the police shot dead the first victim of the Cordobazo, Máximo Mena, which triggered further demonstrations and rioting. Progressively, the population took control of most of the city, setting up barricades to defend themselves. They burnt several administrative centers, as well as the headquarters of the foreign firms, which symbolized Vasena's economic policies, of Citroën and Xerox, although they then accompanied the firefighters in order to impede the fire from extending itself to other city blocks.

On the night of 29 to 30 May 1969, Onganía decided to send the military to crush the uprising. Meanwhile, the headquarters of the CGT de los Argentinos (CGTA, an offshoot of the General Confederation of Labour created in 1968 over opposition to the collaborationist stance adopted by the general secretary of the CGT, Augusto Vandor) were searched and its leaders arrested. Thus, Agustín Tosco, one of the main leader of the CGTA, was arrested and condemned by the War Council.

On the following days, official medias reflected the official vision of the events, allegedly a conspiracy of international communism.

The Cordobazo immediately influenced events in other parts of the country, where violent demonstrations also occurred, and favorised the influence of trade unionists radically opposed to the dictatorship. This latter current, known as sindicalismo clasista, came to head the SMATA trade union of
Córdoba, as well as the autonomous unions of Fiat Concord and Fiat Materfer (SITRAC-SITRAM). Workers' leaders of Córdoba, such as
Agustín Tosco, René Salamanca, Gregorio Flores and José Francisco Páez, played a role on the national political stage. In Salta, Armando Jaime also headed the CGT clasista.

The Cordobazo also had lasting influences on the history of Argentina. On one hand, it showed that the population accepted violent means to defend themselves against the military dictatorship, since no other democratic means of expression could be used. On the other hand, liberal democracy, parliamentarism and the system of elections was globally refused by what came to be known as the New Opposition (Nueva Oposición). Even Arturo Frondizi, who had been elected in 1958, had legitimized the 1955 military coup, known as the Revolución Libertadora, which had toppled Juan Perón.

Finally, the Cordobazo showed Onganía's weakness. He forced his Minister of Economy Vasena to resign, while a transition period opened itself, the military junta, supreme organ of the so-called Revolución Argentina, deciding to depose Onganía of his leadership, replaced in June 1970 by General Roberto M. Levingston, former military attaché at the Argentine Embassy in Washington D.C.. Instead of calling for elections, Levingston decided to go ahead with the Revolución Argentina, governing against the will of the different political parties.

The Opposition's call for elections led to Levingston's replacement by General Alejandro Lanusse, who called for elections but excluded the Peronist Party from participating to it. Lanusse tried to implement starting in July 1971 the Gran Acuerdo Nacional (Great National Agreement), which was to find an honorable exit for the military junta without allowing Peronism participation to the elections. The proposal was rejected by Perón, exiled in Spain, who formed the FRECILINA (Frente Cívico de Liberación Nacional, Civic Front of National Liberation), headed by his delegate Héctor José Cámpora and which gathered the Justicialist Party and the Movimiento de Integración y Desarrollo (MID), headed by Arturo Frondizi. The FRECILINA requested free and unrestricted elections, which took place on March 11, 1973.